The principal purpose of this proposal will be to continue these studies with the objective of defining the relative contribution which humoral and cell-mediated forces may make toward immunity to syphilis. Rabbits or inbred guinea pigs will be made immune by repeated intradermal inoculation with the Nichols strain of T. pallidum. After resistance to reinfection develops serum fractions and/or immunocompetent cells will be collected and transferred to other animals of the same species carrying early, progressing skin lesions. The effect of the passively transferred material(s) on the progression of the lesions should provide evidence of any protective value such materials may possess. Chromatographic methods will be used to fractionate immune sera and buoyant density centrifugation and column absorption techniques will be used to isolate "pure" populations of immune lymphocytes and macrophages. The possible in vitro antitreponemal action of lymphokines will be tested. Another objective is to design measures for enhancing the immune response to vaccines. Adjuvants will be used in an attempt to enhance the immune response in animals infected with live virulent T. pallidum or immunized with a vaccine made by rendering the organism non-infective by storage at 4 degrees C for 7-10 days or by lyophilization. The results may elucidate the nature of immunity and lead to methods for immunization.